Spergualin is a compound which is obtained from a culture broth of Bacillus laterosporus and has antitumor and immunosuppressive effects [cf. U.S. Pat. No. 4,518,532 (Japanese Patent Publication No. 23183/1986) and U.S. Pat. No. 4,416,899 and U.S. Pat. No. 4,851,446 (Japanese Patent Laid-Open No. 48957/1982 and No. 129119/1986)] and there have been synthesized a number of compounds related thereto [cf. U.S. Pat. No. 4,556,735 (Japanese Patent Laid-Open No. 185758/1985), EP-A No. 2-0241797 (Japanese Patent Laid-Open No.45247/1988)]. These compounds are expected to be applicable to drugs such as anticancer agents or immunosuppressive agents.
Although several immunopotentiators have been developed so far, none of them is satisfactory, so that there has been urgently required to develop a novel immunopotentiator. Thus the present invention aims at providing a novel immunopotentiator.